Returning an arrow function from a function

The SphereVolumeFormula function returns an arrow function that computes and returns volume of a sphere of a specific radius r:

function SphereVolumeFormula(r) {
  // returning an arrow function 
  return () => (4/3)*Math.PI*(r*r*r);
}

// Get a volume formula function for a sphere of radius 2
let formula = SphereVolumeFormula(2);

What is the result of calling formula() ?

console.log(formula());